8o Action and Force of the Wedge. [Book L 



therefore, that is, the more acute the angle, the more 

 powerful is its action, and the greater the effects which 

 may be produced by the fame force. 



If the wedge is employed to fplit or to cleave the 

 parts of a hard body which ftrongly adhere together, 

 its advantage is augmented in proportion as the wedge 

 is funk or driven deeper between thefe parts. For 

 fuppcfe two pieces of wcod/^ and / r (fig. 4.) firm- 

 ly connected together by the ftrong bandages p, u, x, 

 &c. all equal in ftrength, and which may reprefcnt 

 the adhcfion of the parts of a billet of wood ; the 

 wedge being placed between the two billets, acts in 

 fome meafure as by the arms//), fp of two angular 

 levers fp q, t pr, while the two other arms pq y pr con- 

 fined by the bandages, mutually fupport each other. 

 If then the force of the wedge exceeds a little that of 

 the firft bandage p, this bandage will be- broken. The 

 fecond bandage , though as tfrong as the firft, will 

 be broken more eafily by the action of the fame wedge, 

 becaufe then the arms of the lever by which it a6ts, 

 are lengthened by the quantity p u y and fo of the 

 ethers. It is doubdefs on this account that hard and 

 dry wood, ftones, glafs, and in general all bodies 

 which are very ftiffor inflexible, break with confider- 

 nble noifc, and cleave or crack upon the firft effectual 

 attempt to cut them. 



All infr.rurnents defigned for cutting or ftabbing, 

 .as kr.ivrs, hatchets, fwords, punches, &c. are claflcd 

 with the wedge. In mort, they have at leaft two in- 

 clined planes, fometimes four or more, which form 

 among them 'an angle more or k-fs acute ; nails, pins, 

 and needles are alfo included in this clafs. 



VI. The SCREW is the lafc of the fix fimple ma- 

 chines which we have to confider, and is a long cone 



or 



